Radio-frequency (RF) tracking is used in many different types of sporting events and for a variety of purposes. In ballgames, RF tags may be attached to players and balls to track their respective movements. In this case, each RF tag is in RF communication with multiple receivers at different respective locations to determine the position of each RF tag. It is also commonplace to equip runners in a race with RF tags for finish line timing, and in some cases for tracking the progress of the runners during the race. RF tracking is also utilized to transmit biometric data of an athlete, such as an athlete's heart rate, by coupling an RF tag with a biometric measurement device carried by the athlete.
In RF tracking, the RF tag attached to the object to be tracked (e.g., athlete, ball, car, etc.) emits a radio signal that is detected by one or more receivers. Based upon the expected speed of movement of the tracked objects, the ping rate (i.e., periodicity, frequency or rate of transmission) from each tag may require between ten and one hundred locates per second. Where many objects are tracked concurrently within the same field of operation, many tags may be configured to transmit frequently, typically resulting in overlap of transmission. This is particularly challenging in events like football where a large number of fast moving objects are tracked to continuously provide position information for each athlete and the ball. In many cases, the quality of location determination is compromised by transmission overlap, often resulting in failure to locate one or more objects. Thus, RF communication limitations impose limits on (a) the number of objects that can be simultaneously tracked and/or (b) the accuracy with which the objects can be tracked.